The intensity and effects of infection with Schistosoma mansoni in a rural community in northeast Brazil
Lehman, J.S.; Mott, K.E.; Morrow, R.H.; Muniz, T.M.; Boyer, M.H.
American Journal of Tropical Medicine and Hygiene 25(2): 285-294
1976
ISSN/ISBN: 0002-9637 PMID: 1259089 Document Number: 107452
The intensity of infection with Schistosoma mansoni and its effects were investigated in a defined population living on 3 contiguous fazendas (subcounties) in a nonmalarious area of northeast Brazil near Salvador, Bahia. Quantitative stool egg counts (Bell technique) were performed on 363 of 417 individuals (90%) of all ages; physical examinations were done on 294 of 357 individuals (82%) 5 years of age and older. The maximum increase in prevalence was observed between the one-to-4 and 5-to-9-year age groups, while the maximum increase in faecal egg count occurred between the 5-to-9 and 10-to-14-year age groups. Highest egg counts were observed in the 10-to-14-year age group (geometric mean of 301 eggs/ml of stool) while the maximum prevalence (100%) was in the 20-to-24-year age group. In the fazenda with the lowest quantitative egg counts the age specific prevalence rates increased more slowly than in the fazendas with higher egg counts. In the study group nearly 50% of the total faecal egg output was accounted for by 22 individuals (6%) who had a mean age of 12.6 years. Egg counts for this selected group were all over 800 eggs/ml of stool with a mean of 1,514 eggs/ml of stool. In children under 15 years of age, the frequency of hepatomegaly and splenomegaly varied directly with the egg count; further, the degree of hepatomegaly was directly correlated with increasing egg counts. No splenic enlargement was noted in children not excreting eggs. In adults, on the other hand, neither splenomegaly nor hepatomegaly could be directly related to schistosomal infection per se. In children, neither the presence of infection with S. mansoni nor its intensity was reflected by altered anthropometric measurements. In the one fazenda tested the frequency of stools positive for occult blood correlated with increasing S. mansoni egg counts. [AS].